A Quantitative Analysis of Plant Community Structure in an Abandoned Rubber Plantations on Kho-Hong Hill, Southern Thailand

ORIGINAL ARTICLE A quantitative analysis of plant community structure in an abandoned rubber plantations on Kho-Hong Hill, southern Thailand Sara Bumrungsri1, Ekapong Sripao-raya2 and Charan Leelatiwong3 Abstract Bumrungsri, S., Sripao-raya, E. and Leelatiwong, C. A quantitative analysis of plant community structure in an abandoned rubber plantations on Kho-Hong Hill, southern Thailand Songklanakarin J. Sci. Technol., 2006, 28(3) : 479-491 The present study aimed to characterize plant community structure of rubber plantations abandoned 26 years previously and now a protected area of Prince of Songkla University on the west slope of Kho-Hong Hill. Trees whose girth at breast high were at least 30 cm were recorded from thirty-one plots (10*10 m) which were laid out systematically at every 100 m along three transects. Among native trees, this plant community is dominated by Schima wallichii Choisy, Castanopsis schefferiana Hance, Memecylon edule Roxb., Diospyros frutescens Blume, and Diplospora malaccensis Hook.f. Trees of the families Myrtaceae, Theaceae, Clusiaceae, Fagaceae, and Rubiaceae, and saplings of Clusiaceae, Myrtaceae, Theaceae, Rubiaceae and Euphorbiaceae were the most common. This plant community was characterized as a late seral stage post-cultivation succession. The basal area of rubber trees was positively significantly related to the species richness of native trees but negatively related to the density of native trees in each plot. Although abandoned rubber plantations create environmental conditions which effectively catalyze forest succession, dense rubber trees could slow succession of native trees by competition for resources. Further ecological, educational and recreational studies are discussed. Zoning this area to be a strict nature reserve and a conservation area is recommended. Key words : rubber plantation, forest succession, secondary forest, Kho-Hong Hill 1Ph.D.(Conservation Biology), 2M.Sc.(Zoology), 3M.Sc.(Botany), Department of Biology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112 Thailand. Corresponding e-mail: [email protected] Received, 26 July 2005 Accepted, 17 November 2005 Songklanakarin J. Sci. Technol. Plant community in abandoned rubber plantation Vol.28 No.3 May - Jun. 2006 480 Bumrungsri, S., et al. ∫∑§—¥¬àÕ “√– ∫”√ÿß»√’ ‡Õ°æß»å »√’‡ª“√¬– ·≈– ®√—≠ ≈’≈µ‘«ß»å ‚§√ß √â“ß —ß§¡æ◊™„πæ◊Èπ∑’Ë «π¬“ßæ“√“∑‘Èß√â“ß∫π‡¢“§ÕÀß å ¿“§„µâ¢Õßª√–‡∑»‰∑¬ «. ß¢≈“π§√‘π∑√å «∑∑. 2549 28(3) : 479-491 °“√»÷°…“§√—Èßπ’È¡’«—µ∂ÿª√– ß§å‡æ◊ËÕ«‘‡§√“–Àå‚§√ß √â“ß —ß§¡æ◊™„πæ◊Èπ∑’Ë «π¬“ß∑’Ë∑‘Èß√â“ß¡“ 26 ªï∫√‘‡«≥‡™‘ß ‡¢“§ÕÀß å ´÷Ëß‡ªìπ‡¢µÕπÿ√—°…å∏√√¡™“µ‘¢Õß¡À“«‘∑¬“≈—¬ ß¢≈“π§√‘π∑√å ∑”°“√«“ß·ª≈ß¢π“¥ 10x10 ‡¡µ√ ∑ÿ°Ê √–¬– 100 ‡¡µ√µ“¡‡ âπ·π« 3 ‡ âπ «—¥¢π“¥·≈–®”·π°™π‘¥µâπ‰¡â∑’Ë¡’¢π“¥‡ âπ√Õ∫«ß∑’Ë√–¥—∫Õ°µ—Èß·µà 30 ´¡. ¢÷Èπ‰ª æ∫«à“‰¡âæ◊Èπ‡¡◊Õß∑’Ë¡’§à“¥—™π’§«“¡ ”§—≠ Ÿß§◊Õ ¡—ßµ“π (Schima wallichii Choisy) °àÕ‡¢’È¬«À¡Ÿ (Castanopsis schefferiana Hance) æ≈Õß‡À¡◊Õ¥ (Memecylon edule Roxb.) æ≈—∫°≈â«¬ (Diospyros frutescens Blume) ‡¡◊ËÕ æ‘®“√≥“„π√–¥—∫«ß»åæ∫«à“ «ß»å∑’Ë‡¥àπ§◊Õ «ß»å Myrtaceae Theaceae Clusiaceae Fagaceae ·≈– Rubiaceae ¢≥–∑’Ë ≈Ÿ°‰¡â„π«ß»å∑’Ëæ∫¡“°§◊Õ«ß»å Clusiaceae Myrtaceae Theaceae Rubiaceae ·≈– Euphorbiaceae ªÉ“∑¥·∑ππ’Èπà“®– Õ¬Ÿà„π√–¬–°“√∑¥·∑π¢—Èπ∑â“¬ ¢π“¥¢Õßæ◊Èπ∑’ËÀπâ“µ—¥√«¡¢Õß‰¡â¬“ßæ“√“¡’§«“¡ —¡æ—π∏å∑“ß∫«°°—∫§«“¡À≈“°™π‘¥ ¢Õß‰¡âª√–®”∂‘Ëπ·µà¡’§«“¡ —¡æ—π∏å∑“ß≈∫°—∫§«“¡Àπ“·πàπ¢Õß‰¡âª√–®”∂‘Ëπ„π·ª≈ß»÷°…“ ∂÷ß·¡â«à“ «π¬“ß∑’Ë∑‘Èß √â“ß®–¡’ ¿“æ·«¥≈âÕ¡∑’Ë™à«¬‡√àß°“√øóôπµ—«¢ÕßªÉ“µ“¡∏√√¡™“µ‘ µâπ¬“ßæ“√“∑’ËÀπ“·πàπÕ“®®–≈¥§«“¡‡√Á«¢Õß°“√ øóôπµ—«¢Õß‰¡âªÉ“‚¥¬°“√·°àß·¬àß∑√—æ¬“°√ ‡π◊ËÕß®“°¡’°“√„™âæ◊Èπ∑’Ëπ’È‡æ◊ËÕ°“√»÷°…“∑“ßπ‘‡«»«‘∑¬“ ‡ªìπ·À≈àß‡√’¬π√Ÿâ ·≈–‡æ◊ËÕ —π∑π“°“√ ®÷ß§«√·∫àß°“√„™âæ◊Èπ∑’Ë‡ªìπ‡¢µ ß«π·≈–‡¢µÕπÿ√—°…å ¿“§«‘™“™’««‘∑¬“ §≥–«‘∑¬“»“ µ√å ¡À“«‘∑¬“≈—¬ ß¢≈“π§√‘π∑√å Õ”‡¿ÕÀ“¥„À≠à ®—ßÀ«—¥ ß¢≈“ 90112 Throughout the tropics, enormous areas of Kho-Hong Hill, the largest isolated forest primary forest have been converted to agricultural remnant close to the city of Hat Yai, was once land and this phenomenon is a major contributor covered with tropical forest, however, the majority for biodiversity loss (Bryant et al., 1997). In some of the hill area (>50%) is currently covered by instances, cultivated land is abandoned and replaced rubber plantations. During 1976-1980, Prince of by secondary forest. Although it differs from Songkla University bought some rubber plantations, original forest, this post-cultivation secondary and sixty hectares of them had no further disturb- forest supports a number of forest taxa, even when ance or cultivation, so that secondary forest became isolated from intact forest. Like other tropical established. This secondary forest is now protected countries, Thailand has lost a large portion of its as the university's nature reserve. This protected forest in the last few decades. Fifty three percent forest is a catchment for water supply to the of the country's area was covered with forest in university and has become increasingly used for 1961, but this had declined to 33.15% in 2000 research, education, recreation, and plant conserv- (Department of National Park, Wildlife and Plant ation. An inventory carried out by Maxwell (1986) Conservation, 2003). Rubber or 'yang-pa-ra' indicated relatively high diversity of at least 596 (Heavea brasiliensis Willd. ex A. Juss.) plantations, species of vascular plants on this hill. Several the major cultivation practice in southern Thailand, undergraduate research projects have been done in replace large tracts of tropical forest. Rubber the area, mainly on animals such as birds, termites, plantation increased from 1.58 million ha in 1978 ants and canopy beetles (Charoensap, 1996; to 2.0 million ha in 1992. In that year, 25% of the Ratcharote, 1999; Sritangnan, 1999; Wattanasit et area of southern Thailand was covered with rubber al., 2005). Further research on forest regeneration, plantations whereas only 18% was forest (Royal other ecological studies and nature interpretation Forest Department, 1993). are planned (Prince of Songkla University, 2002). Songklanakarin J. Sci. Technol. Plant community in abandoned rubber plantation Vol.28 No.3 May - Jun. 2006 481 Bumrungsri, S., et al. However, the area is still lacking a quantitative Division, 1973). Bedrocks are heavily crushed and description of the forest community. It is also weathered carboniferous mudstones (Maxwell, important to describe the community structure of 1986). abandoned rubber plantations of known age, since it may provide insights into the process of forest Methods recovery. In addition, it is interesting to establish the extent to which a high density of planted rubber Plots of 0.01 ha (10*10 m) were laid out trees affects the establishment of native plants. The systematically at every 100 m along three transects objectives of the present study are to describe the (800-1200 m long) in a North-South direction community structure of the secondary forest in an (Figure 1). Transects were 150 m apart. When plots abandoned rubber plantation, and to determine the were placed on slopes, their size was adjusted by relationship between the density of rubber trees and x = 10tan φ where x is the adjusted length, and φ the density and diversity of native plants. is the degree of slope. Trees whose girth at breast high (1.3 m) (GBH) was at least 30 cm were Study area identified and recorded for their GBH. Saplings and shrub (GBH less than 30 cm but greater or The present study was carried out in a equal to 5 cm) were identified and counted in a protected forest of Prince of Songkla University on 4*4 m subplot set at the south-west corner in each Kho-Hong Hill (07º 00.4' N, 100º 30.7' E.). This plot. Voucher specimens of unknown species were isolated hill lies in a North-South direction and is collected for later identification by comparing surrounded by settlements and agricultural land. with specimen in the Prince of Songkla Herbarium. Most of the study area (60 ha) was an abandoned Aspect and location of each plot were also noted. rubber plantation mixed with a disturbed forest. A number of quantitative attributes were These plantations had been abandoned since they calculated. These were density (D) (total number were bought by the university during 1976-80. The of tree of species x/total sampling area), frequency study area is characterized with slight undulating (F) (number of plots with species x/ total number terrain ranging in altitude between 30 and 100 m of plots), dominance (basal area of species x). The asl, situated on the western side of the hill. The contribution of each species to the forest community summit rises to 371 m. Former rubber plantations in relation to other species was determined as covered most of the lower elevations and flat areas. relative density (Rden) (density of species x/ density The 10 years climate was hot (mean minimum- of all species), relative frequency (Rf) (frequency mean maximum temperatures = 24.1-32.5ºC, of species x/ sum frequency of all species), relative average 28.3ºC) and relatively humid (average dominance (Rdo) (basal area of species x/ basal area relative humidity of 72%) with 2,118 mm mean of all species). The performance of each species annual rainfall. Generally, there was a three month was determined from the sum of relative contri- dry season (February to April) with rainfall less butions referred to as the Importance Value Index than 100 mm, whereas rain was heavy in October- (IVI) when IVI = Rden + Rf + Rdo. December (Kho-Hong Meteorically Station, 2004). A profile diagram of trees in a selected This tropical climate is classified as tropical wet 10x30 m plot was drawn and the composition and seasonal according to Walsh (1996).

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